Sex Differences and Physical Activity Status on the Hamstring: Quadriceps Ratio, Activities of Daily Living, and Functional Movement in Older Adults.

The study aimed to investigate sex differences and the effect of physical activity on the hamstring:quadriceps (H:Q) ratio, activities of daily living (ADLs), and the Functional Movement Screen (FMS) in older adults. Thirty older adults (72.56 + 6.22) completed maximal voluntary isometric contractions (MVICs), ADLs, the FMS, and three closed-kinetic chain exercises (CKCs); front lunge (FL), side lunge (SL), and bilateral squat (BLSQ). Electromyography was recorded from the biceps femoris (BF) and vastus lateralis (VL) on the dominant and non-dominant limbs during the MVICs and CKCs. Raw EMG recordings were normalized to MVICs and analyzed for root mean square (RMS). The H:Q ratio was calculated using RMS as BF/VL. It was determined that males had significantly higher H:Q ratios during the FL (p = 0.002), SL (p = 0.012) and BLSQ (p = 0.023), as well as higher RMS of the BF during the FL (p = 0.031), SL (p = 0.01), and BLSQ (p = 0.042). Females scored higher on the ADLs and FMS. A significant positive correlation was observed between ADLs and RMS of the VL (p < 0.05, r > 0.40), whereas a negative correlation was observed between ADLs and RMS of the BF (p < 0.05, r < -0.5). The results suggest that males may activate their hamstrings more effectively than females and that females may tend to remain quadriceps dominant. High motor unit recruitment of the hamstring muscles may coincide with reduced functional ability, whereas high motor unit recruitment of the quadriceps may coincide with enhanced functional ability.

Tumor necrosis factor-α, TNF receptor, and soluble TNF receptor responses to aerobic exercise in the heat.

The purpose of this study was to evaluate the effects of aerobic exercise in the heat on circulating concentrations of tumor necrosis factor (TNF)-α, soluble TNF receptors (STNFR1&2), and surface expression of TNFR1&2 on monocyte subpopulations. Twelve recreationally active Caucasian men (24.4 ± 3.4 yrs.; 180.0 ± 6.8 cm; 81.5 ± 8.0 kg; 47.2 ± 4.8 mL·kg-1·min-1) completed an exercise protocol in three environmental conditions: high temperature/low humidity [HTLH; 35 °C, 20% relative humidity (RH)]; high temperature/moderate humidity (HTMH; 35 °C, 45%RH); and moderate temperature/moderate humidity (MTMH; 22 °C, 45%RH). Each protocol consisted of a 60-minute cycling trial at 60% VO2max, a 15-minute rest, and a time-to-exhaustion trial at 90% VO2max (TTE). Blood was sampled before (PRE), immediately after (POST) the 60-minute trial, immediately post-TTE (PTTE), and one-hour post-TTE (REC). Circulating TNF-α and STNFR1&2 were assayed. TNFR1&2 expression on monocyte subsets was measured by flow cytometry on a subset of participants (n = 8). TNF-α area under the curve with respect to increase (AUCi) was greater during HTMH compared to MTMH and HTLH. STNFR1 concentration was greater during HTMH compared to MTMH. With all trials combined, STNFR1 concentration increased from PRE to POST, PTTE, and REC. TNFR1 expression on non-classical monocytes was greater during HTMH compared to HTLH while TNFR2 expression was lower during HTLH compared to both MTMH and HTMH. Data suggest that exercise in the heat increases circulating TNF-α and STNFR1 concentration concomitantly. Furthermore, non-classical monocyte expression of TNFRs are impacted by temperature and humidity during exercise.

Investigating Effects of Cold Water Hand Immersion on Selective Attention in Normobaric Hypoxia.

This study investigated the effect of cold-water hand immersion on selective attention as measured by the Stroop Color Word Test in nomorbaric normoxia and hypoxia. Ten healthy men rested for 60 min, after which they immersed their non-dominant hand into 5 °C water for 15 min. The interference score of the Stroop Color Word Test and thermal sensation were measured at baseline in the final 5 min of resting and in the final 5 min of cold water hand immersion. The interference score was not influenced by hypoxia but was found to be significantly improved compared to resting in both conditions during cold water hand immersion. Selective attention improved during 15 min of cold-water hand immersion, with increased thermal sensations rated as "very cool" of the immersed arm. Cold-water hand immersion may be helpful in improving cognitive function in normoxia and normobaric hypoxia.

Cold-induced vasodilation responses before and after exercise in normobaric normoxia and hypoxia.

PURPOSE: Cold-induced vasodilation (CIVD) is known to protect humans against local cold injuries and improve manual dexterity. The current study examined the effects of metabolic heat production on cold-induced vasodilation responses in normobaric hypoxia and normoxia. METHODS: Ten participants immersed their non-dominant hand into 5 °C water for 15 min. Minimum finger temperature (Tmin), maximum finger temperature (Tmax), onset time, amplitude, and peak time were measured before and after exercise under normoxia (21% O2) and two levels of normobaric hypoxia (17% O2 and 13% O2). RESULTS: Neither Tmin nor amplitude was affected by hypoxia. However, Tmax was significantly decreased by hypoxia while reduction in onset time and peak time trended towards significance. Tmin, Tmax, and amplitude were significantly higher during post-exercise CIVD than pre-exercise CIVD. CONCLUSION: The CIVD response may be negatively affected by the introduction of hypoxia whereas metabolic heat production via exercise may counteract adverse effects of hypoxia and improve CIVD responses.

The Effect of Inspiratory Resistance on Exercise Performance and Perception in Moderate Normobaric Hypoxia.

Seo, Yongsuk, Jeremiah Vaughan, Tyler D. Quinn, Brittany Followay, Raymond Roberge, Ellen L. Glickman, and Jung-Hyun Kim. The effect of inspiratory resistance on exercise performance and perception in moderate normobaric hypoxia. High Alt Med Biol. 18:417-424, 2017. PURPOSE: Respirators are simple and efficient in protecting workers against toxic airborne substances; however, their use may limit the physical performance of workers. The purpose of this study was to determine the effect of inspiratory resistance on physical performance and breathing perception in normobaric hypoxia. METHOD: Nine healthy men wore a tight-fitting respiratory mask outfitted with one of four different inspiratory resistors (R) (0, 1.5, 4.5, 7.5 cm H2O/L/Sec) while exercising at normobaric hypoxia (17% O2) at submaximal exercise workloads of 50, 100, and 150 W on a cycle ergometer for 10 minutes each, followed by a maximal oxygen uptake (VO2max) test to exhaustion. RESULTS: Maximal power output at R7.5 was significantly lower than R0 (p = 0.016) and R1.5 (p = 0.035). Respiration rate was significantly reduced at R4.5 (p = 0.011) and R7.5 (p ≤ 0.001) compared with R0. Minute ventilation was significantly decreased in R7.5 compared with R0 (p = 0.003), R1.5 (p = 0.010), and R4.5 (p = 0.016), whereas VO2 was not significantly changed. Breathing comfort (BC) and breathing effort (BE) were significantly impaired in R7.5 (BC: p = 0.025, BE: p = 0.001) and R4.5 (BC: p = 0.007, BE: p = 0.001) compared with R0, but rating of perceived exertion (RPE) remained unchanged. CONCLUSIONS: Added inspiratory resistance limited maximal power output and increased perceptions of BC and BE in normobaric hypoxia. However, low-to-moderate inspiratory resistance did not have a deleterious effect on VO2 or RPE at submaximal or maximal exercise. Perceptual and physiological characteristics of respirators of varying inspiratory resistances should be considered by manufacturers and end users during design and respirator selection processes.

Age-related effects on maximal and rapid hamstrings/quadriceps strength capacities and vertical jump power in young and older females.

BACKGROUND AND AIMS: Declines in hamstrings and quadriceps maximal and rapid strength are commonly reported as a consequence of aging; however, few studies have investigated the influence of age on maximal and rapid hamstrings to quadriceps (H/Q) strength ratios. This study aimed to examine the effects of age on leg extension and flexion maximal and rapid torque production, H/Q strength ratios, and muscle power in healthy, young and old females. METHODS: Fifteen young (21 ± 2 years) and 15 old (69 ± 7 years) females performed 3 isometric leg extension and flexion maximal voluntary contractions (MVCs), from which peak torque (PT), early (0-30 ms) and late (0-200 ms) phase rate of torque development (RTD), and PT and RTD H/Q strength ratios were extracted. Lower-body peak power output (P max) was assessed through a vertical jump test. RESULTS: P max, PT, and early (RTD30) and late (RTD200) RTD variables of the leg extensors and flexors were lower (P ≤ 0.048) and PT and RTD200 H/Q strength ratios were higher (P ≤ 0.030) in the old compared to the younger females; however, no difference was observed for RTD30 H/Q (P = 0.300). There were also significant negative relationships in the older (r = -0.616 and -0.522; P = 0.014 and 0.046) but not the younger (r = 0.295 and -0.109; P = 0.286 and 0.698) females between P max and RTD30 and RTD200 H/Q strength ratios. CONCLUSION: The higher RTD200 H/Q ratio for the older females may contribute to the muscle power deficits often observed in elderly populations. Practitioners may use these findings to help identify older adults with low muscle power capacities and possibly overall functional decline.